This invention relates to certain new and useful improvements in two-wheeled hand trucks of the type used to transport relatively heavier loads which are of such bulk and weight that it is not practical to attempt to carry them without vehicular assistance. Among patents which relate generally to hand trucks of this character are the hand trucks illustrated in the following U.S. patents:
______________________________________ 1,452,135 1,965,944 2,710,106 2,080,332 4,121,855 2,096,994 4,275,894 2,607,606 4,563,014 ______________________________________
Several of the above patents are owned by the present inventor's assignee, and, as noted in U.S. Pat. No. 4,275,894, for example, the loads to which a hand truck is subjected can vary within wide limits, and the loads will have a wide range of centers of gravity, dependent upon the shape, bulk and heft of the product being carried. Normally hand trucks of this type, which are used for a wide variety of purposes, including transporting kegs of beer, cases of soft drinks, and baggage, for example, provide wheel-supporting brackets which are fixed to the hand truck frame. Hand trucks which are designed with a particular use in mind can be designed to best handle a load having a known center of gravity, but will not handle as well for loads having considerably different centers of gravity.
One of the prime objects of the present invention is to provide a more versatile hand truck which has a manipulatable wheel structure which can move from a first position adjacent the lower end of the frame for handling loads with a relatively low center of gravity, to a second rearwardly removed position for handling loads with a relatively higher center of gravity.
A corollary object of the invention is to provide a hand truck which is inherently balanced, when in operation with the wheeled structure in either of the positions mentioned.
A further object of the invention is to provide a hand truck of this character which utilizes overcomeable, yieldable, resistance exerting members operating through a predetermined moment arm to releasably lock the wheel structure in one or the other positions relative to the frame.
Still another object of the invention is to provide a hand truck of the character described which is supported for rolling movement solely by the wheel structure, and does not require the use of additional supporting wheels in either of the positions in which the hand truck is used.
Still a further object of the invention is to provide a heavy duty hand truck of the character described which does not depend upon mechanical latches or similar devices which need to be manipulated by the user for maintaining the repositionable wheel structure in either of its positions, the hand truck at all times being, for practical purposes, automatically locked in either of the positions.
Other objects and advantages of the invention will become apparent by reference to the following specification and to the drawings.